Change "mydomain" when setting up Active Directory login to Portal for ArcGIS

[JasminePrater]

I recently setup our first Portal for ArcGIS, version 11.1, and after I added the recommended code in the User Store Configuration to setup Active Directory login, I realized that all of our Portal usernames are going to be a really odd combination of our AD usernames and that domain.  Imagine "username@GOTHAM_CITY"  versus "username@gothamcity.com" for our Portal usernames.  

Our AD domain is hybrid Azure AD joined and our Sys Admin said the "@gothamcity.com" domain name should be interchangeable.  Unfortunately, I don't know much about AD and he doesn't know much about GIS, so I'm hoping someone might be able to provide some insight on how we can change the domain name in the User Store Configuration.  We already use the email addresses for user logins in AGOL, so I'd prefer to keep them the same when we transition to Portal.

I have already tried to change it directly in the User Store Configuration, but it gave me an error.  When I changed it back to the original domain, it worked again.

[ReeseFacendini]

The Active Directory connection for user accounts would need to be replaced with a SAML provider connection, which sounds like is what's currently configured in ArcGIS Online. Because your org is already setup with Azure AD, it shouldn't be too difficult to make that change in Portal.

When doing that, all user accounts would have to be recreated, and any content transferred from username@GOTHAM_CITY  to username@gothamcity.com